1. I could see Movie-Odin resorting to abandoning the Earth if he feels like he has no other choice. I remember on how in "Thor 1", Odin mentioned on how much he had to sacrifice in the past in order to maintain the overall peace, and given his ancient age, this is probably a person who has gotten used to having to make big sacrifices if push came to shove.

2. Rather than being exiled, I could see Thor choosing to leave Earth, in a similar manner that "Earth's Mightiest Heroes" had done when Thor left Asgard at the beginning on his own free will after getting into a argument with Odin. Thor's development as a character could eventually evolve through the course of the next Avengers and Thor film (Thor 3) where Thor realizes that Earth is well enough in capable of hands of defending itself and that he doesn't need to be there as much as a result.